I'll start by saying that I've posted a similar post elsewhere on the wonderful wacky web, but I thought I'd post here to get a US take on this...apologies therefore, if you have already seen this elsewhere...

I'm about to collect a (completely stock) 1600 '75 bay camper with what has been described as having an 'intermittent engine failure'.

The information I have is that it starts idles and runs well...giving no indication of any issues. This I can confirm, having seen the engine start and test driven it. However, on a longer drive - after 10 miles, or so (sometimes as few as 5, sometimes more than 20) - apparently the motor cuts out and refuses to re-start. Then, after leaving it for a quarter of an hour or so, it will start up again and go a bit further. What I don't know(yet) is how it behaves when the motor dies.

My initial thought was that the coil was on its way out...failing as it warms up, then recovering temporarily, if it is left to cool. Additional potential causes that have been suggested so far are: carb-ice & a fuel supply problem - blocked filter, hose or tank exit nozzle...

I would be interested to hear any thoughts on other potential causes of this...fuel related?...mechanical...? or even confirmations of the above theories!

I fully appreciate that I haven't given much in the way of detail of the symptoms...but I would have thought the fact that it behaves perfectly normally for a time would help rule would out many potential culprits...carb adjustment/jetting, air leaks, timing, etc...?

I will have to drive the car home tomorrow evening, which will give me the opportunity to gather some more data. At this point, I plan to do the following before I drive it home:

Swap the coil for one I know is good

Fit a new fuel filter (and potentially replace all the fuel lines for new, if I can find enough pipe in my parts store - not sure how feasible this would be though, on the side of the road!!)

Fit an anti carb-ice sleeve

I figure these 3 will either: 1) if the problem is solved, narrow down the actual cause to 3 possibilities or 2) if the problem is not solved, eliminate 3 potential causes. Either way, this is good.

Cheers in advance for any suggestions/observations!

Paul

PS, If you are wondering why I'm buying a bus with an 'iffy' motor...its almost rust free, which us rare in the UK, with our internationally famous hot & sunny climate...!

when changing the filter inspect the inlet for rust particles that could hint to a rusty tank. Also inspect the wires going to the coil when you replace it, My fathers bug did that to me once where it would start and drive then just die I kept thinking fuel but it turned out that one of the wire's to the coil was hanging on by a strand and would heat up and increase resistance causing the car to die and act like it was running out of fuel. one other potentially problematic part is the ignition switch, though it typically causes a no start not a dieing after running, too many keys on an owners ring stress the electrical portion of the switch and over time cause it to fail.

I successfully drove the camper home on Friday & while the predicted problems did occur, I managed to keep the motor going and got home in one go.

It turns out that the problem is an intermittent misfire, as opposed to a complete engine failure as I had originally thought. It is present up to about 50mph, but not above. I found that when the misfire started to happen, if I eased off the gas a little it stopped fairly quickly and I could start to build up speed again.

I will be completely replacing the fuel lines and filter and I'll install a freshly cleaned carb (I have a spare). The motor has aleady had everything that can be replaced on the engine, replaced by the previous owner, including the wiring loom in the engine compartment, with the exception of the rubber inlet manifold connectors...which I will do myself as they are looking cracked...can't harm. I'll of course check the timing and adjust as needed, though I've been told this has already been done...

More digging & poking around later and I have visually inspected & confirmed that the whole run of fuel line from the tank has been recently replaced, as have the coil, HT leads, Dizzy cap, points & plugs.

I will still need to remove the tank to replace the faulty sender, at which time I'll renew all the junctions in the breather/vapour recovery system (I've already found a broken join where it runs through the the diagnostic port bracket) as well as the filler neck/pipe. I figure I may as well do the full job once, as opposed to a half the job multiple times...

It's a brand new mechanical pump, the later style, with all new fuel line & a new filter. I can't speak for the in-tank filter though, or the state of the tank itself. I should be able to get at the tank this evening, to have a look.

This intermittent misfire has occurred (so far, in my experience) for maybe 10-30 seconds at a time, about every 5-10 mins and only while driving at speeds below about 50 mph.

so...progress...engine is out, or at least on the floor in the engine bay.

I now have access to the tank and have inspected all the breather pipe joins and replaced the 2 that were shot (the remainder and the tank itself look in excellent condition). Ironically, the 2 that needed to be replaced were in the engine bay!!

Next task will be to remove the tank so I can replace the exit pipe & filter, the sender and inspect the inside - yes.. I realise that a pristine outside can easily hide a gunky inside!. I also have the carb stripped, in anticipation of a rebuild kit arriving in the post.

And, not surprisingly, I've discovered a bunch of other jobs that need to be sorted...CV joint gaiters, for example and the heater box controls and...the list goes on!

The parts I've been waiting for finally arrived yesterday, so I spent the evening completing the process of replacing all the rubber in the fuel system. Once I had the tank out (which needed to come out anyway, to replace the sender) I was able to inspect the inside which was almost spotless. Even the gauze filter on the exit pipe looked new - not bad after 40 years! Anyway, all the filler pipe rubber is now new, as are all the breather pipe joins & the hose from the tank.

This evening's task will be to replace the firewall, re-fit the engine and finally to clean, rebuild & reinstall the carb.

All the old rubber has now been replaced, though on actual inspection almost all of the old rubber was still good...even the inside of the tank looks virtually pristine - certainly no sludge blocking the exit. However, given the fuel these days, new rubber can't be a bad thing.

The tank & engine are now back in, but after spending an hour trying to wiggle the motor back in to place & persuading the fiddly nut on the starter bold to go on, I'd found that the throttle cable is trapped in the tinware...engine off again! I wouldn't mind so much, but I was careful to thread the cable through the tinware and into the tube (through the fan shroud) specifically to avoid this happening....I guess it must have worked its way out as I was wiggling the motor home...

...guess my job for this evening after work...good thin I enjoy all this!!

I had similar symptoms with a '76 Capri. Someone had poured biocide in the tank. It was alcohol soluble, so I rinsed the tank with alcohol, which loosened up 10 years of scale in the tank. For two months, I'd drive it for a few days until the giant temporary filter clogged, pull the filter and blow it out, and then press on. The GF loved the gasoline breath....

I had similar symptoms with a '76 Capri. Someone had poured biocide in the tank. It was alcohol soluble, so I rinsed the tank with alcohol, which loosened up 10 years of scale in the tank. For two months, I'd drive it for a few days until the giant temporary filter clogged, pull the filter and blow it out, and then press on. The GF loved the gasoline breath....

Biocide?

To kill all those pesky bugs that live in gasoline in the dark?
(I know its possible on diesel and jet fuel in certain environments, but haven't heard of gasoline having an algae or bacterial issue)

Cool that she's running, thanks for the follow up.

I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...